1. Field of the Invention
The present invention relates to an imaging device, and more specifically, it relates to processing executed on a value to be used for an imaging operation in the imaging device.
2. Description of Related Art
In a single lens reflex camera, part of the subject light flux departing an imaging lens toward an image forming plane is guided to a photometering sensor and a focus detection (range finding) sensor to enable calculation of the photometering value and the range value for the subject. The imaging lens may allow the imaging optical system to be shifted or tilted relative to the image forming plane. When capturing an image with such an imaging lens with the imaging optical system in a shifted or tilted state, the photometering operation and the focus detection operation cannot be accurately executed since the angle of incidence of the subject light flux at the photometering sensor or the focus detection sensor is altered from the angle of incidence that is measured when the imaging optical system is not shifted or tilted. Japanese Laid Open Patent Publication No. H9-21943 discloses an optical device that calculates a range value once the extent of shift or tilt of the imaging lens becomes equal to or beyond a predetermined value by using a correction value that has been stored in advance corresponding to the extent of the shift or tilt.
However, in the optical device disclosed in the publication described above, too, the range value is corrected by using a predetermined correction value, which means that the resulting range value is not completely accurate. In other words, if the extent of decentering of the incident subject light flux due to the shift or the tilt is outside an allowable range at the focus detection sensor unit, the range finding operation cannot be executed.